Barrier operator systems of the type including a barrier operator and associated drive assembly for opening and closing sectional garage doors typically also use a counterbalance assembly to provide additional force to assist in the raising of the door and to effect control over the lowering of the door. This assembly conventionally includes a large compression spring for providing the necessary force and a pair of spaced support cables that are attached at one end to the counterbalance spring shaft and at the other end at the bottom of the door. After extended periods of use and/or in instances where the garage door is operated without any preventative maintenance, different portions of the counterbalance assembly can be susceptible to wearing out or breaking, and in some circumstances potentially create unintended movement of the door unless this potential is adequately addressed. For example, this could potentially occur if one or the other of the two support cables snap while the door is closing, due to the then uncounterbalanced weight of the door. In such event, a method of resisting unintended movement of the door can provide additional safety for people and property in the vicinity of the opening.
Many solutions have heretofore been developed to attempt to address this problem. Many of the devices designed to prevent door movement are bulky, difficult to install, costly, not easily retrofitted onto an existing door, or otherwise not satisfactory in their operation for many conditions of service. A need therefore has existed for a new and improved safety device to protect against unintended movement of the door in the event of the breaking of, or damage to, the counterbalance assembly or significant portions thereof.